Predictive Speed Control With Short Prediction Horizon for Permanent Magnet Synchronous Motor Drives

In this paper, a predictive speed controller (PSC) based on finite control set model predictive control is developed for electric drives. The large difference between the mechanical and electrical time constants necessitates long prediction horizons for a direct PSC (DPSC) strategy to be implemented. Therefore, the computation burden for online solving of the optimization problem critically increases even for low-complexity topologies, whereas the DPSC implementation becomes impossible for high-complexity inverters. Additionally, due to the absence of a PI controller in DPSC methods, stability issues arise; therefore, special care is mandated for eliminating steady-state errors. By using proper weighting of the speed errors, along with the current errors, in the cost function of the proposed PSC, the use of many prediction steps becomes unessential. For considering the current dynamics, a linear controller is incorporated in the control law of developed PSC offering improved system behavior, whereas the consideration of the speed errors allows achieving fast response characteristics. The proposed strategy is experimentally evaluated through examining reference and disturbance step changes of a PMSM drive with the three-level neutral-point clamped inverter. Finally, the proposed controller operation is experimentally compared with a predictive torque and speed control, by considering several performance indices.